Grow BumpPtrAllocator's slab size dynamically if we allocated many slabs. This

[oota-llvm.git] / lib / Support / Allocator.cpp

diff --git a/lib/Support/Allocator.cpp b/lib/Support/Allocator.cpp
index 90df262336c59a36ddb4e3c11fbab39e32ce25c0..02b45d8af98f1be8dd80b76fb1fbd297e59e026a 100644 (file)
--- a/lib/Support/Allocator.cpp
+++ b/lib/Support/Allocator.cpp
@@ -44,6 +44,12 @@ char *BumpPtrAllocator::AlignPtr(char *Ptr, size_t Alignment) {
 /// StartNewSlab - Allocate a new slab and move the bump pointers over into
 /// the new slab.  Modifies CurPtr and End.
 void BumpPtrAllocator::StartNewSlab() {
+  // If we allocated a big number of slabs already it's likely that we're going
+  // to allocate more. Increase slab size to reduce mallocs and possibly memory
+  // overhead. The factors are chosen conservatively to avoid overallocation.
+  if (BytesAllocated >= SlabSize * 128)
+    SlabSize *= 2;
+
   MemSlab *NewSlab = Allocator.Allocate(SlabSize);
   NewSlab->NextPtr = CurSlab;
   CurSlab = NewSlab;